drm/vmwgfx: Make sure backup_handle is always valid

commit 07678eca2cf9c9a18584e546c2b2a0d0c9a3150c upstream.

When vmw_gb_surface_define_ioctl() is called with an existing buffer,
we end up returning an uninitialized variable in the backup_handle.

The fix is to first initialize backup_handle to 0 just to be sure, and
second, when a user-provided buffer is found, we will use the
req->buffer_handle as the backup_handle.

Reported-by: Murray McAllister <murray.mcallister@insomniasec.com>
Signed-off-by: Sinclair Yeh <syeh@vmware.com>
Reviewed-by: Deepak Rawat <drawat@vmware.com>
[bwh: Backported to 3.16: There's no size check after vmw_user_dmabuf_lookup(),
 so only check ret == 0.]
Signed-off-by: Ben Hutchings <ben@decadent.org.uk>

diff --git a/drivers/gpu/drm/vmwgfx/vmwgfx_surface.c b/drivers/gpu/drm/vmwgfx/vmwgfx_surface.c
index 17c78638f34ace78eefb755e3faa64d7e546ed0c..22f94030d995dd20131f00fbe6f91f944f57525c 100644 (file)
--- a/drivers/gpu/drm/vmwgfx/vmwgfx_surface.c
+++ b/drivers/gpu/drm/vmwgfx/vmwgfx_surface.c
@@ -1245,7 +1245,7 @@ int vmw_gb_surface_define_ioctl(struct drm_device *dev, void *data,
        int ret;
        uint32_t size;
        const struct svga3d_surface_desc *desc;
-       uint32_t backup_handle;
+       uint32_t backup_handle = 0;
 
        if (req->mip_levels > DRM_VMW_MAX_MIP_LEVELS)
                return -EINVAL;
@@ -1317,6 +1317,8 @@ int vmw_gb_surface_define_ioctl(struct drm_device *dev, void *data,
                ret = vmw_user_dmabuf_lookup(tfile, req->buffer_handle,
                                             &res->backup,
                                             &user_srf->backup_base);
+               if (ret == 0)
+                       backup_handle = req->buffer_handle;
        } else if (req->drm_surface_flags &
                   drm_vmw_surface_flag_create_buffer)
                ret = vmw_user_dmabuf_alloc(dev_priv, tfile,